Thread tensioning device and mechanism for actuating the same



2,562,]. 75 ANISM y 1951. F. E. COLE THREAD TENSIONING DEVICE AND MECH FOR ACTUATING THE SAME 2 Sheets-Sheet l Filed Sept. 29, '1948 rhw m w & m E r 0 .11 F I m m L I 0 a z G m W. G M l |..ml |l 1 0 Lwm w w m n. w w r o 4 5 July 31, 1951 F. E. COLE THREAD TENSIONING DEVICE AND MECHANISM FOR ACTUATING THE SAME 2 Sheets-Sheet 2 Filed Sept. 29, 1948 inventor Frank E. Cole Patented July 31, 1951 new NSIO N DEVICE AN E ANISM For. ACTUATING T SAME Frank LCole, Manchester,- Mass, assignor to Un t d Shoalarbit C porat on, H m n '1'|0.n,,N. J- atcmfhp 'ation (pf-New Jersey Application September 29, 1348, Serial No. 51,712

granted March 12, 1949; and United .States Let! ters Patent :No. 2,359,662, granted October .3, 1944, upon application of Alfred B. Merrill.

The sewing machine of:the application and patent, above identified, is operated to attach a welt and upper to the insole of a lasted shoe. In machines of this type, besides the curved'hook needle, the stitch forming devices comprise an oscillating take-up acting successively duringeach sewing cycle to give up thread for the for.- mation of each stitch, to tighten and set the stitch by exerting a predetermined tension on the thread and thereafter to draw from the supply'sufficient thread for the formation of the succeeding stitch. The tension is applied by a device connected with the take-up acting to impart maximum resistance to thread movement during the action of the take-up in tightening and setting each stitch. The tensioning device of'the machine illustrated in thesaid Patent No. 2,465,356 comprises a :traction member in the form .of .a pair .of toothed disks providing between them azperipheral groove within which-the thread passes and .a friction brake drum connected to the traction member. To resist rotationlof the brake drum with the traction memher, in the machine of Patent No.'2,465,'356, the drum is surrounded by a multi-coil spring braking band of an internalsize slightly smaller than the diameter of the :brake drum and so mounted that the band normally grips the drum by its own inherent force with an initial pressure which is first automatically increased progressively along the length'of the band .as the drum is turned; The'jband then begins to turn with the drum. When'the tension on the thread reaches a edetermined int s y the b aking band finally is actuated by engagement with an abutment :to

cause it to reduce its ,grip progressively along the :band, maintaining the thread under vuniform tension,-tnereaf;ter, as the traction member moves. The :amountof tension in the thread also is controlled throughout each sewing cycle by con ectin one en .01 the braking band to the taksmprwh h, While a stit h :is bein set, increases the initial pressure of the band on the drum. 1 so doing, an additional pressurexisaap- .1 Q1aims- (01.11215 plied periodically to the braking band beyond that obtained in its initial position surrounding the shaft and the pressure is reduced after each stitchis set.

:While the arrangement .of a coil spring braking banddisclosed in the said Patent 'No. 2,465,- 356 is effective for the purposes intended, it has been found that there is a tendency under 10ertain conditions for vibratory action between .the ends of the band andwide variations -:in dimentions and strengths occasionally are foundbetier-exit spring bands as a result of manung inequalities, thus affecting adversely the -u lior-inity of thread tension obtainable with this type of thread tensioning device.

An object of the present invention is to simplify the construction and improve the mode of operation of :a thread ltensioning device for .a shoe' sewing machine.

Another object of the present invention is to provide a sewing machine with a thread tensioning-device of the type referred to comprising a traction-member land a brake drum connected with the traction member and surrounded by a coil spring braking band arranged in such a way that vibratory tendencies and manufacturing inequalities are substantially reduced and, as a result, it is possible to keep the tension on the thread more uniform and reliable under all circumstances than has been found possible here-- tofore.

A still further object of the invention is to improve the construction of a coil spring braking band particularly for use with a sewing machine but also for other applications whenever uniformity of action andlease of adjustment are essential. In this connection the invention has for its purpose the provision of a coil spring braking band which may readily be manufactured on 'a production basis with substantial uniformity of results in use, both in applying a braking action to-a bralze drum as well'as' in re leasing the braking band from such engagement as willoffer any substantial resistance to rotation of thedrum.

To the ends above set forth the present invention is-embodied in a hook needle shoe sewing machine having a loopen'means acting to tighten each :stitch and to draw thread from the supply past a tensioning device comprising a traction member :and ab-rake drum, in which a coil spring braking :band engages the brake drum to resist its rotation-only when the band :is stressed by an outside force against the brake drum, the band :being formed with a dimension .to enable free rotation of the brake drum when no stress is applied to the band. By this construction, a predetermined pressure of the band against the drum and-a positive release of the band from frictional engagement with the brake drum are more readily obtained than heretofore, it being possible to construct a spring band with a uniform normal unstressed shape by easy manufacturing procedure such that no binding action on the drum will occur while the stress on the band is released and yet for a given relative movement between the ends of the band a predetermined pressure will be exerted on the drum. This construction is an improvement over that of inventors prior Patent No. 2,465,356, above referred to, in which it is necessary to stress the Spring band in order to release it from the drum, inasmuch as in stressing the band to release it the alinement of the coils in the band may be upset to such an extent as to prevent complete release from a close fitting drum. This feature of the invention includes the use of a shock absorbing connection for the band actuating mechanism. Such connection reduces irregularities in the thread tension, particularly when tension is applied suddenly to the thread or when there is a tendency to set up a jerky :periodic vibration in the band or its actuating mechamsm.

' Heretofore, machines of the type above referred to have been constructed to apply two intensities of tension to the thread. Another feature of the present invention, which is particularly useful with a coil spring braking band type of thread tensioning device, but which is of more general application with any other form of thread tensioning device, relates to mechanism for actuating the tensioning device to apply two or more different intensities of tension to the thread. In the illustrated machine beneficial results have been obtained by applying at least three definite degrees of tension to the thread during each sewing cycle and for some purposes a substantial release of all tension is advantageous at least once in each sewing cycle in order to bring the thread and the thread engaging devices uniform- 1y to a predetermined unstressed relationship regardless of lost motion, yield and friction in the machine.

- Other features of the invention consist in the devices, combinations and arrangements of parts hereinafter described and claimed which, together with the advantages to be obtained thereby, Will readily be understood from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a view in left side elevation of the upper forward portion of a chainstitch shoe inseam sewing machine illustrating a preferred embodiment of the invention and indicating the parts in stopped positions;

Fig. 2 is a time chart of the tension controlling mechanism;

Fig. 3 is a view in left side elevation, similar to that of Fig. 1, showing the positions of the parts while the machine is running;

Fig. 4 is a sectional plan view of a portion of the thread tensioning device and take-up of the machine looking in the direction of the arrow IV in Fig. 3; and

Fig. 5 is a detail sectional View on an enlarged scale of a tension actuating and controlling plunger in the machine, taken along the line V-V of Fig. 1.

The shoe sewing machine illustrated in the '4 l drawings is provided with the usual stitch forming devices of a welt or turn inseam sewing machine comprising a curved needle 4, a looper 6, a thread finger I, a take-up 8, a welt guide 10, a channel guide l2, and a back rest [4. During operation of the machine the needle enters the work, the thread is laid in its hook by the looper, and the take-up gives up thread to the needle during its retracting stroke. Thereafter the work is fed a stitch length and the needle again enters the work, passing through the loop formed during its first work entering movement and the take-up sets the stitch by tightening the loop about the shank of the needle. After setting each stitch, the take-up draws thread past a tensioning device sufificient in length to form the succeeding stitch. The parts thus briefly referred to and their actuating mechanisms are, except as hereinafter described, of the same construction and mode of operation as in the machine'of inventors application and the Morrill patent above referred to. The machine of the patents, however, is an automatic machine as distinguished from the present hand controlled machine in which the machine is started and stopped and the shoe presented by an operator;

The thread tensioning device of the present machine, as in the machine of the application and patent, comprises a traction member consisting of a pair of toothed disks l6 secured together and to a rotatable shaft I8 to provide a grooved tension wheel about which the thread passes from the supply (not shown) to the stitch forming devices. In the machine of inventors Patent No. 2,465,356 rotation of the tension wheel is resisted frictionally by an elongated braking band wrapped about a brake drum secured to the tension wheel shaft. In that machine the braking band consists of a coil spring having a pluralitp of turns so constructed that its normal internal diameter is less than that of the brake drum which it engages so that itmust be expanded to bring it into surrounding relation to the brake drum. In order to control the frictional braking pressure of the prior spring band;

to release the drum properly, different spring bands having difierent characteristics in this re-' spect even though close attention is given during their manufacture and essential heat treat.- ment.

To avoid difficulties in manufacture of a tension wheel braking band consisting of a plurality of turns of coil spring wire, such as employed in the machine'of inventors Patent No. 2,465,356;

according to a feature of the present invention, the illustrated tension wheel shaft I8 has secured to one end a tension wheel drum 20 in the fOIl'liOf a sleeve fixed to the shaft and the braking band, in the form of a wire coil spring, indicated at 22, is illustrated as having seven turns surrounding the brake drum. For best results it has been found that the use of seven to twelve turns is effective. The normal inside diameter of the coil spring 22 is slightly greater than the external diameter of the brake drum and the ends of the spring extend in a generaldirection radially to'the drum. Accordingly, when the bralging band is actuated to apply africtional pressure on the drum, it is given a spring stress by the application of a predetermined external fprcebetween radially disposed ends of the spring in a direction to wind up the coils and tighten them into engagement with the drum. To re,- lease the spring from the drum it is only neces saryto permit the spring to expand to its normal size by removing the spring stressing force. If the spring is originally manufactured with its coils in alinement, a uniform releasing action always will occur without any tendency tocause a frictional resistance to be imparted to the drum 22. Furthermore, the only manufacturing requirement in the production of such a coil.

the present machin and to bring the sprin into uniform frictional engagement with the drum 2!], the forwardly directed leading end, considering the drum as winding up the spring, is engaged in the notch of a block 24 secured by a bolt 26 to an arm 28 rotatably mounted on a pin 30 carried by the frame of the machine. To support the leading end of the spring against the rotating action of the tension wheel brake drum during operation of the machine, the arm 28 remains stationary. The rearwardly directed trailing end of the spring is connected to actuating mechanism for stressing and releasing th spring. For this purpose the trailing end of the spring passes diametrically through an actuating and controlling plunger 32 slidably mounted for reciprocation is a guide 34 clamped to the machine frame to, direct-movements of the plunger transversely to and at one side of the axis of the tension wheel shaft l8 and of the brake drum mounted thereon.-

Th mechanism for stressing and releasing'the spring includes the plunger 32 which extends through the frame of the machine and is held yieldingly in a downward direction to maintain a cam follower roll 35 at its lower end in engagement with the open face of the four-position cam 38 secured to a sewing shaft 40 in the machine. The plunger 32 constitutes a carrier for the cam roll 36 and is pressed downwardly by a compression spring 52 retained within a sleeveshaped boss A l projecting upwardly from the machine frame. At the upper end of the boss 54 is a screw plug 46 acting against the upper end of 5 the spring, the lower end of the spring surrounding the upper end of the plunger and bearing against a shoulder formed by a reduced portion ofthe plunger within the spring.

In some instances, particularly when a relative- 1y light frictional force is being exerted by a braking band comprising a coil spring, it has been found. that there is a tendency for the spring. to vibrate or to be subject to sudden shock move-. ments which impair uniformity of retarding action on the brake drum surrounded thereby. As a. result, irregularities, ,in thread tension. and. stitchformation may occur.

i To avoid variations in threadtension as a result of vibratory movements and irregular frictional drag of the illustrated braking band, the leading and trailing ends'of the band 22 have. a shock absorbing connection with the block 24 and the-plunger 32, respectively, the notch inthe block fl engaging and supporting the Ieadingend of;

the spring in such a way that frictionalsliding movement occurs between the spring and the block as the leadingendof the spring is bowed and straightened instressing and releasing the saddle by an anvil 52 yieldingly mountedin the plunger. The anvil 52 forms the upper enlarged end of a pinsurrounded by a coil spring 54 compressed betweenethe lower end of the slot 48 in the plunger and the anvil. The strength of the sprin 54 is such as to maintain the spring 22 constantly in engagement with the saddle, re-

gardless of the position of: the plunger but with a decreasing pressure as the frictional engagement of thecoll spring 22 is increased on the brake drum 20. The plunger moves in a straight line path but the trailing end of the spring moves in an arcuate path about the brake drum, thus causing frictional sliding between the spring and the saddle 41. With anincrease of frictional pressure of the spring on the brake drum, a greater proportion of the vibration or tendency to vibrate is absorbed by direct frictional action against the brake drum, whereas with relatively small frictional pressure on the brake drum a greater proportion of the vibratory tendency in the band is absorbed between the saddle and anvil of the actuating and controlling plunger.

The four position cam 38 for controlling the tensioningfmeans is formed with a high bulging portion 56 (Fig. 1) to increase the tension on the thread to a maximum intensity while each; stitch is being set, a lower portion 58 to decrease the tension on the thread to a minimum intensity during the action of the looper in laying the thread in the'hook of the needle and a portion 60 betweenthe bulging and lower portions, of a height to apply tension intermediate the maxi- -mum and minimum intensities during eachvretractin -stroke -of the "needle. The cam is also provided with aYportionfiZ of a height less than that of the portior'r'fill and is so formed that all of the stressin. the spring 22 will be released at that time in each sewing cycle after the needle has been retracted to disengage it from the work and after the take-up has set each stitch. It is at this time in a sewing cyclein which the machine also is brought to rest by a stopping mechanism thread tension in pounds plotted against the rotation ofzthe main sewing shaft in degrees. At the startin position of the main sewing shaft the stress, in the braking band is released so that no tension is applied to the thread for the first five degrees. Thereafter the maximum tension of approximately A0 pounds is applied during the take-upstroke; ofthe take-up. It is at this time that the needleengages the work and at the end of the take-run stroke a new loop of thread is laid. inithe. hook of theneedle and the thread finger, is: actuated to measure, sufficient thread; to enable thethreadedineedle to be retracted from the work} without causing the thread to slidein theneedle 7 hook. During the looping and measuring movements the tension is reduced to approximately five pounds. The needle then retracts from the work and at the end of the retracting movement the thread tension is increased to the intermediate intensity of fifteen pounds so that a previously formed stitch will be tightened securely. As the needle again starts to move toward the work the tension is entirely relieved, no tension being ape-- plied until the next succeeding sewing cycle. 7 If the machine is brought to rest during the time of thread tension release it is possible to remove the shoe from the machine without withdrawing the the stitches inserted by reason of the pull of the thread remaining in the machine. Further than this, all of the thread engaging parts are relieved of forces of reaction ordinarily produced by the tension on the thread so that there is an opportunity for them to seek their naturally related unstressed positions before the start of the new sewing cycle. Such release of thread tension is of advantage in correcting any tendency toward overthrow of the thread engaging parts during the formation of each stitch.

Whenever the machine is brought to rest, substantially all of the stress is released from the spring brake band 22 by the control plunger acting on the trailing end of the spring and in order to avoid any possibility of frictional pressure between the band and the drum 20 the leadingend of the band also is disengaged from the support of the block 24 by connections with the stopping mechanism, as illustrated in Fig. 1. For this pur pose the arm 28 on which the block 24 is mounted has a downwardly extending lug 68 engaged by a rod 'Hl slidingly mounted at it upper end in the machine frame and pivotally connected at its lower end with the stop arm 64. Movement of the stop arm while the cam roll thereon is entering the slot 66 forces the arm 28 in a direction to disengage the block 24 from a supporting position for the spring. To return the parts to operative position when the machine is restarted the upper end of the arm 28 is acted upon by a compression spring 12 mounted between the machine frame and the arm. Movement of the arm 28 by the spring is limited by the engagement of the lu 68 with the upper surface of the machine frame (as shown in Fig. 3). a dot-dash line, indicated at 14, connecting the point of engagement of the block 24 with the spring 22 and the pivot 30 is substantially at right angles to the portion of the spring engaging the block.

To shift the point of engagement of the block 24 with the spring 22 to suit the operating conditions and the characteristics of the spring 22particularly when more or less turns are employed. the bolt 26 passes through a slot 16 (see Fig. 4)

extending in the block 24 lengthwise of the brake drum 20. The bolt 26- is threaded into engagement with a slide 18 carried by a guideway in the arm 28. The position of the slide 18 along the arm 28 transversely of the brake drum 20 is readily shifted by means of a thumb adjusting screw 80 threadedly received by an opening in the arm and having a collar engaging a slot in the undersurface of the slide 18. Movement of the slide 18 along the arm 28 not only affects the released position of the forward end of the spring 22 but also increases or decreases the effective length of the forwardly projecting end of the spring, thusproviding means to compensate for a change in' the wire size or stiffness of the spring in a de-' sirable manner.

In this position of the arm The nature and scope of the invention having been indicated, and a particular embodiment having been described, what is claimed is:

1. A shoe sewing machine having stitch forming devices includin a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a thread traction member, and a brake drum connected to the traction member, in combination with a coil spring braking band of a normal inside diameter greater than the external diameter of the brake drum, a plurality of turns of which engage the brake drum to resist its rotation when the band is stressed against it.

2. A shoe sewing machine having stitch forming devices including a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a thread traction member, and a brake drum connected to the traction member, in combination with a coil spring braking band of a normal inside diameter greater than the external diameter of the brake drum, a plurality of turns of which engage the brake drum to resist its rotation when the band is stressed against it, and mechanism for stressing the band to engage, the drum during. each sewing cycle while the tightening means is acting.

3. A shoe sewing machine having stitch forming devices including a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a thread traction memher, and a brake drum connected to the traction member, combination with a coil spring braking band of a normal inside diameter greater than the external diameter of the brake drum, a plurality of turns of which engage the brake drum to resist its rotation when the band is stressed against it, and mechanism for stressing the band to engage the drum during each sewing cycle while the tightening means is acting and for releasing the stress after the needle is disengaged from the work.

4. A shoe sewing machine having a main sewing shaft, stitch forming devices including a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a thread traction member, and a brake drum connected to the traction member, in combination with a coil spring braking band of normal internal diameter greater than the external diameter of the brake drum, a plurality of turns of which band engage the brake drum when the band is stressed, and mechanism for stressing and releasing the hand during each sewing cycle comprising a cam on the sewing shaft and a cam follower operatively connected to one end of the band.

5. A shoe sewing machine having a, main sewing shaft, stitch forming devices including a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a

thread traction member, and a brake drum connected to the traction member, in combination with a coil spring braking band of normal internal diameter greater than the external diameter of the brake drum, a plurality of turns 6. A shoe sewing machine having a main sew ing shaft, stitch forming devices including a hook i'needle, a looper, 'means acting :to tighten". each stitch and to draw thread from the supply, a

thread tractionmembergand a brake drum connected to the traction member, in combination and a saddle on the plunger engaging frictionally with the band to absorb vibratory movements of the band. U

'7. A shoe sewing machine having a main sewing shaft, stitch forming devices including a, hook needle, 2; looper, means acting to tighten each stitch and to draw thread from the supply, a thread traction member, and a brake drum connected. to the traction member, in combination with a coil spring braking band of normal internal diameter greater than the external di ameter of the brakedrum, aplurality of turns of which band engage the brake drum When the band is stressed, and mechanism for stressing and releasing the band during each sewing cycle comprising a cam on the sewing shaft, a plunger connected to one end of the brake band. at one :side of the axis of rotation of the brakedrum,

a saddle on the plunger engaging frictionally with the band, and a yielding anvil in the plunger for pressing the hand against the saddle to absorb vibratory movements of the band.

8. A shoe sewing machine having a main seW- ing shaft, stitch forming devices including a, hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a traction member and a brake drum connected to the traction member, in combination with a coil spring braking band, a plurality of turns of which engage the brake drum, mechanism acting on one end of the band for stressing and releasing the band during each sewing cycle, and mechanism connected to the other end of the band for releasing the stress on the band when the machine is brought to rest.

9. A shoe sewing machine having a main sewing shaft, stitch forming devices including a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a tract-ion member and a brake drum connected to the traction member, in combination with a coil spring braking band, a plurality of turns of which engage the brake drum, mechanism acting on one end of the band for stressing and releasing the band during each sewing cycle, and mechanism connected to the other end of the band for releasing the stress on the band when the machine is brought to rest comprising a pivoted arm, and a block on the arm engaging one end of the band arranged to move toward and from a position with the line connecting its point of engagement with the band and its pivot at right angles to that portion of the band engaging the block.

10. A shoe sewing machine having a main sewing shaft, stitch forming devices including a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a traction member and a brake drum connected to the traction member, in combination with a coil spring braking band, a plurality of turns of which engage the brake drum, mechanism acting on one end of the band for stressing andreleasing the band during each sewing cycle, and mechanism connected to theother end of the band for releasing the stress on the band when the machine is brought to rest comprising a pivoted arm, a block on the arm engaging one end of the band arranged to move toward and from a position with the line connecting its point of engagement with the band and its pivot at right angles to that portion of the'band engaging the block, and yielding means for retaining said arm with the band in its right angle relation.

11. A shoe sewing machine having a main sewing shaft, stitch forming devices including a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a'traction memberand a brake drum connected to the traction member, in combination with a coil spring braking band, a plurality of turns of which engage the brake drum, mechanism acting on one end of the band for stressing and, releasing the band during each sewing cycle, and mechanism connected to the other end of the band for releasing the stress on the band when the machine is brought to rest comprising a pivoted arm, a block on the arm engaging one end of the "band arranged to move toward and from a position with the line connecting its point oi engagement with the band and its pivot at right angles to that portion of the band engaging the block, yielding means for retaining said 'arm' with the band in its right angle relation,' and a connection for actuating the arm against the force of the yielding means to release the band.

12. A shoe sewing machine having stitch forming devices including a hook needle, a looper, means acting to tighten each stitch and to draw thread from the supply, a thread traction member, and a brake drum connected to the traction member, in combination with a coil spring braking band, a plurality of turns of which engage the brake drum, mechanism connected to one end of the band to apply a heavy tension on the thread while each stitch is being tightened, to decrease the tension on the thread while the looper lays the thread in the needle hook and to decrease still further the tension on the thread when the threaded needle is disengaged from the work, and mechanism connected to the'other end of the band for releasing all the stress on the band when the machine is brought to rest.

13. In a machine for handling thread having devices acting to draw thread from a supply, a traction member moved by the thread and a brake drum connected to the traction member, in combination with a coil spring braking band, a plurality of turns of which engage the brake drum and one end of which projects radially from the brake drum, means for stressing the band against the brake drum comprising an arm, a block on the arm having a slot extending lengthwise of the brake drum, a clamp bolt in the slot to enable the position of the block to be shifted along the drum.

, the brake drum comprising an arm, a slide on the arm, a block on the slide engaging the band and means for shifting the slide along the arm to enable the effective length of the projecting portion of the band to be increased or decreased.

15. A shoe sewing machine having stitch forming devices including a hook needle, a looper, a take-up acting to tighten each stitch and to draw thread from the supply, and thread tensioning means, in combination with mechanism for actu ating the tensioning means to at least three positions to apply a heavy tension on the thread while each stitch is being set, to decrease the ten sion on the thread while the looper is acting to lay the thread in the hook of the needle and to apply a tension to the thread intermediate the stitch setting and looping intensities during each retracting stroke of the threaded needle.

16. A shoe sewing machine having stitch forming devices including a hook needle, a looper, a take-up acting to tighten each stitch and to draw thread from the supply, and thread tensioning means, in combination with mechanism for actuating the tensioning means comprising a cam having a high bulging portion to increase the tension on the thread to a miximum intensity while each stitch is being set, a lower portion to decrease the tension on the thread to a minimum intensity thereafter and a portion of a height between the bulging and the lower portions to apply a tension to the thread intermediate the maximum and minimum intensities during each retracting stroke of the needle.

17. A shoe sewing machine having a main sewing shaft, stitch forming devices actuated thereby including a hook needle, a looper, a take-up acting to tighten each stitch and to draw thread 12 from the supply, and thread tensioning means, in combination with mechanism for actuating the tensioning means to increase the tension on the thread to a maximum intensity while each stitch is being set, to decrease the tension on the thread to a minimum intensity thereafter and to apply tension to the thread intermediate the maximum and minimum intensities during each retracting stroke of the needle comprising a cam on the sewing shaft and a member actuated by the cam connected to the tensioning means.

18. A shoe sewing machine having stitch forming devices including a hook needle, a looper, a take-up acting to tighten each stitch and to draw thread from the supply, a thread traction memher, a brake member connected to the traction member and a spring braking band having a, plurality of turns engaging the brake drum, in combination with mechanism for actuating the braking band comprising an open cam, a cam roll and a yieldingly actuated carrier for the roll connected to the one end of the band.

FRANK E. COLE.

REFERENCES CITED UNITED STATES PATENTS Name Date Cole Mar. 29, 1949 Number 

